The invention relates to a permanent magnet rotor for an electric motor, as well as to a method for manufacturing such a permanent magnet rotor.
With permanent magnet motors, permanent magnets are arranged in the rotor, distributed over the periphery. Block-like permanent magnets are applied for an as inexpensive as possible construction of the rotor, and these extend parallel to the rotation axis of the rotor in the inside of the rotor. This arrangement has the disadvantage, that the course of the torque of the motor has undesirable peaks or waves. In order to achieve a more uniform torque course, it is known to form free spaces or grooves in the rotor, in the region of the edges of the permanent magnets, and the magnetic flux is interrupted or reduced in their course. The grooves are designed in a helical manner or running in an oblique manner, in order thus to achieve a more uniform torque course. Grooves formed on the outer periphery of the rotor however lead to a larger air gap between the rotor and the stator, and thus to a loss of efficiency.